<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script src="https://unpkg.com/vue@next"></script>
<div id="app">{{count}}</div>

<script>
    const vueOpt = {
        data(){
            return {

            }
        }
    }

    const app = Vue.createApp(vueOpt);
    const vm = app.mount("#app");

    // data外的属性，vue系统不会自动跟踪它。
    vm.count = 10;
</script>
</body>
</html>
